About Percentage Calculator

Calculate percentages, discounts, tips, and markup. Part of the DevTools Surf developer suite. Browse more tools in the Calculators collection.

Use Cases

• Calculating discount amounts for e-commerce feature testing
• Figuring out tip splits at team lunch outings
• Computing markup percentages for pricing engine validation
• Determining percentage change between deployment metrics

Tips

• Switch between modes for discount, tip, and markup
• Enter the original and final values to find percent change
• Use the tip calculator mode for quick dining math

Fun Facts

• The percent sign (%) evolved from a shorthand for 'per cento' in 15th-century Italian manuscripts, gradually losing the words until only the symbol remained.
• Sales tax was first introduced in West Virginia in 1921, making percentage calculations a daily necessity for Americans.
• The concept of compound interest — percentages on percentages — was described by Luca Pacioli in his 1494 book 'Summa de Arithmetica'.

FAQ

What kinds of percent problems?

Find X% of Y, what percent is X of Y, and percent change (old → new). Three common scenarios in one tool.

Increase or decrease?

Percent change handles both. Positive = increase; negative = decrease. Absolute and relative changes shown.

Percent vs percentage points?

Different! From 10% to 12% is 2 percentage points OR 20% relative increase. The tool shows both to avoid confusion.

Compound percentages?

A 10% increase followed by 10% decrease is NOT zero net — it's -1% (1.1 × 0.9 = 0.99). The tool catches this common mistake.